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Name: Steve Stampfli
Date Sighted: February 12, 2008
Location: Husum, Washington, residence along the White Salmon River and Rattlesnake Creek.
Date Posted: February 19, 2008
Time Posted: 8:03 am
SIGHTING:
While un-stacking wood for the woodstove this week, I was startled by a hiss from the pile that could have been small rattlesnake or other tough customer. After carefully removing another couple of pieces, I found a roosting or hibernating little brown bat (Myotis lucifugus) that was in partial torpor, but still up to bearing some angry teeth. Feeling guilty for dismantling his hibernating space, I moved him to another pile of firewood that I knew would not be burned this winter. Fifteen minutes later, I looked out the living room window and noticed the ever active Bob (cat) knocking something around. It was the little brown who had unexpectedly straggled out of his new quarters. Severe threats and stick-waving got the Bob to move away, while I rescued the bat once again. This time I brought the bat inside to a box for overnight rest, while I tried to figure what I could do to get him back to some safe winter roost.
Photo 1. Little brown bat (Myotis lucifugus).
A search of the internet led to no good practical instruction on how to nurse and care for distressed bats. I learned only to stay far from them for fear of rabies, and the usual instruction to call in a certified bat rehabilitation expert from Seattle or some such. In further searching, I learned that only a fraction of 1% of bats carry rabies, and that there is need for much more practical, applied and un-sanitized information on the internet from bat conservation organizations.
That night I puzzled over where to place the little brown for final recovery and continued hibernation. It would need to be a place that somewhat mirrored his temperature, humidity and air circulation needs, as well as protection from marauders. I did find some info on this via the internet, determining that little brown bat winter hibernacula typically consist of caves, rock crevices or in the thermal mass of big tree trunks. This immediately led to thinking of my house foundation, and cool late fall days when I had found little browns hunkered tightly against the concrete inside crawl space vents. A potential recovery room idea for the little brown came to mind.
The next day, I went about designing and building a “foundation vent insert bat box”, intended to provide recovery, winter hibernation and roosting habitat. I thought that once the box was installed in the vent, it would be thermally connected to the large mass of the house foundation and benefit from the consistently moderate (45 degree F) and moist air from the crawl space.
The following pictures give an idea of how I eventually designed and installed this seemingly new type of bat habitat structure.
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Photo 2. First step in constructing “foundation vent insert bat box” shell and baffles, showing the interior (crawl space) end of box. Since the foundation vents are screened on the rear, there is no possibility of bats entering the crawl space or upstairs of residence. Safe from the dreaded rabies!
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Photo 3. Second step in constructing foundation vent bat box, and attachment of the outside cedar “face boards” to provide a 3/8” entry slot and for sealing against face of foundation.
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Photo 4. Last step in constructing “foundation vent insert bat box”, showing application of small cedar block against rear of baffles to moderate air flow and provide mostly enclosed and stable spaces. Would a better design consist of horizontally placed baffles, or no baffles with one large chamber?
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Photo 5. Final step of installing the foundation bat box on south-facing side of residence. The box is designed for friction fit, to enable easy removal in late spring for unrestricted crawl space ventilation. This also allows maintenance and monitoring of chiroptera (i.e., bat, and from the greek roots “chiro” (hand), and “ptera” (wing)). Is it a good idea to mount such boxes on the south facing exposures, or might heating from winter sun cause bats to get overly active during the period they should be hibernating?
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Photo 6. Completed installation of foundation vent box with recovering little brown bat (Myotis lucifugus) placed inside. The installation is immediately intended as a recovery room for the bat, but may find future use by other chiroptera for winter hibernation (hibernacula), or even summer day/night roosting.
In conclusion, it will be interesting to monitor how the new box works. If the recovering bat is found dead inside next spring, I’ll know that the immediate purpose wasn’t achieved. Next summer, I’ll build a “double vent“ version of the box designed with two side-by-side inserts connected by common face boards. This system could then be installed in the ten paired foundation vents around all sides of the house. As mentioned in the 5th photo caption, the thermal conditions are undoubtedly very different on all sides of the north/south oriented house, due to different sun exposures. Temperatures could be easily charted using small temperature loggers, which could then be compared to what boxes get the most use. One might also experiment with leaving some boxes in over the summer, to see if they get used for day and night summer roosting. The only concern with this is the near-ground location of the vents, and possible predation by animals during bat entry and exit. It would not take the determined Bob much time to figure out their routine.
Want to chat with Steve about this design? Email him!